Byron David Smith told investigators with the Morris County Sheriff's Office that he fired on 17-year-old Nicholas Brady Schaeffel with a Ruger Mini 14 rifle Thanksgiving Day as the youth descended the stairs to Smith's basement.

Smith said he fired an additional, fatal blow after Brady fell down the stairs. The suspect said he had been in his basement workshop and heard the sound of breaking glass on the main floor of the house, followed by the sound of foot steps.

According to the criminal complaint Smith said he shot Brady's 18-year-old cousin Haile Kifer several minutes later as she walked down the same set of stairs. Smith told deputies he shot Kifer several more times with a pistol after his rifle jammed.

He did not call authorities to report the shootings. The following day, Smith called a neighbor to inquire about finding a criminal attorney. The neighbor notified authorities.

"The biggest misconception is that self-defense law is something simple, that would fit on a bumper sticker," John Caile, a firearms instructor for 40 years, told KARE.

"I spend a good three and a half hours on just the legal part in my classes, which is more than a lot of people do."

He says those who buy weapons to defend themselves in their homes need to understand in Minnesota there's no such thing as automatic immunity from prosecution for shooting another person.

"So there's no duty to retreat inside your house. That does not mean that your house is a free fire zone, and you get to shoot anyone who walks through the door," Caile explained.

"It's one of the few times where you walk into court, freely admitting you did it, and now you have to explain to the jury why they should not send you to prison."

The prosecution still has the burden of proving that the shooting wasn't justified, but defendants in self-defense cases often face what's known as the "burden of production" -- to produce evidence backing their perspective.

It states, "The intentional taking of the life of another is not authorized except when necessary in resisting or preventing an offense which the actor reasonably believes exposes the actor or another to great bodily harm or death, or preventing the commission of a felony in the actor's place of abode."

The state's instruction guide for jurors in deadly force cases also uses similar terminology. When the incident takes place in the shooter's home the legal hurdles are easier to meet.

But the jury guide lays out the following three conditions, for the killing to be justifiable:

The defendant's action was done to prevent the commission of a felony in the dwelling

The defendant's judgment as to the gravity of the situation was reasonable under the circumstances

The defendant's election to defend (his/her) dwelling was such as a reasonable person would have made in light of the danger perceived.

All three of those conditions must be met, but again the word "reasonable" is subject to varying interpretations.

"At the end of the day 12 people in the jury box are going to be the ones that decide if that law applies to you, and if so how much."

Wisconsin's new Castle Doctrine lawcarries a "presumption of immunity" from criminal prosecution for people acting in self-defense at home, in their cars or places of businesses.

That is defined, for purposes of that law, as "reasonably believe that the force was necessary to prevent imminent death or great bodily harm." This applies to cases in which the shooting victim is in the process or forcibly entering the home, or was already present in the home illegally.

Even that law cannot be perceived as a license to kill at will, Caile said. He said common law on self-defense and justifiable homicide will still allow persons to be prosecuted if the circumstances fit.

In 2011 Gov. Mark Dayton of Minnesota vetoed a bill that would've spelled out deadly force self-defense rights more specifically, including a presumption of reasonableness. It would've also explicitly removed the "duty to retreat" in areas away from a person's home.

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